Method for controlling operation of a blast furnace

ABSTRACT

A method for controlling heat conditions in a blast furnace wherein the heat conditions are inferred and judged in comparison of data output from sensor means provided for the blast furnace with knowledge base means formed by accumulated experience on the operation of the blast furnace. The heat conditions are inferred and judged from levels of heat conditions and from levels of transition of heat conditions, wherein data regarding molten metal temperature and those regarding sensors are used. The inference and judgement are carried out by inference engine means included in a small-scale computer.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part-application of Ser. No. 45,126 filed onApr. 30, 1987, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for controlling operation of ablast furnace, and more particularly, to a method for controlling heatconditions in the operation, based on information outputted from sensormeans provided for the blast furnace.

2. Description of the Related Art

It is well-known, as a method for controlling temperature of moltenmetal tapped out of a blast furnace, by means of estimation of thetemperature, to persons in the art, that operational factors arecontrolled to optimum, by means of evaluating furnace operationconditions, on the basis of qualitative judgement on informationoutputted from sensor means provided for the blast furnace.

Japanese Examined Patent Publication (KOKOKU) No. 30007/76, for example,describes a method for controlling blast furnace operation, wherein, inorder to carry out optimum operation by means of amending a long cyclechange appearing during computer control of blast furnace operationconditions, heat balance of the blast furnace operation is controlled bymeans of humidity of blast air blown in through tuyeres. The humidity isdetermined by an equation modified by an amendment member of preventingSi-content in molten metal from making a long cycle change. Theamendment member is determined by an amount of direct reduction computedfrom measured values which are continuously obtainable during the blastfurnace operation.

This method, however, is disadvantageous in that it requires an analysismodel to be maintained by means of modification thereto in compliancewith the changes the blast furnace undergoes through its life. Inaddition, the modification itself is quite a time-consuming andcomplicated task, as the analysis model is quite complex.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method forcontrolling heat conditions in blast furnace operation, wherein ananalysis model can easily be modified in compliance with the changeswhich the blast furnace undergoes during its life.

According to the present invention, a method is provided for controllingoperation of a blast furnace, wherein the blast furnace includes asensor means which outputs first data, corresponding to conditions insaid blast furnace which comprises the steps of:

supplying a central processing unit with said first data outputted fromsaid sensor means;

storing standard data corresponding to predetermined values of datacorresponding to said conditions in said blast furnace;

preparing true-and-false data by comparing said firs data with saidstandard data;

storing information on operation and control characteristics of saidblast furnace based on accumulated actual knowledge and experience of atleast one operator of said blast furnace, said information being storedas data in a knowledge base means;

inferring and judging heat conditions in the blast furnace, on the basisof said true-and-false date and said data in said knowledge base meansand formed by accumulated experience on the operation of the blastfurnace; and

controlling heat conditions in the blast furnace in accordance withresults of said inferring and judging step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation illustrating a method forcontrolling heat conditions in a blast furnace according to the presentinvention;

FIG. 2 is a schematic block representation showing an apparatus forperforming the method of the present invention;

FIG. 3 is a flow diagram showing the method of the present invention;

FIG. 4 is a flow diagram showing inference and judgement processaccording to the method of the present invention;

FIG. 5 is a flow representation showing a step method of judging levelsof heat conditions in the blast furnace according to the presentinvention;

FIG. 6 is a flow representation showing a step method of judging levelsof transition of heat conditions in the blast furnace according to thepresent invention;

FIG. 7 is a flow representation of weighing levels of furnace heatconditions according to the present invention;

FIG. 8 is a flow representation of weighing levels of transition offurnace heat conditions; and

FIG. 9 is a graphic representation showing an example of the results ofthe blast furnace operation according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment according to the present invention will now be described,with reference to FIGS. 1 to 4.

FIG. 1 schematically represents a method for controlling heat conditionsin a blast furnace according to the present invention. Reference numeral10 denotes a large-scale computer. Computer 10 includes sequentialprocessing means 12 which processes sequentially the data outputted fromsensor means 11, sequential filing means 13, sensor-data processingmeans 14 and interface buffer means 15. Reference numeral 20 denotes asmall-scale computer, which includes knowledge base means 21 for judgingheat conditions of the blast furnace, knowledge base means 22 forjudging actions in response to the heat conditions, common data buffermeans 23 and inference engine means 24. Reference numeral 30 denotes acathode ray tube (CRT), which displays the results calculated by theinference engine means. Reference numeral 31 denotes control deviceswhich control heat conditions in the blast furnace.

FIG. 2 schematically illustrates an apparatus for performing the methodaccording to the present invention. Reference numerals 11a, 11b and 11ceach indicate sensors corresponding to sensor means 11 shown in FIG. 1.Large-scale computer 10 includes the following devices:

41: interface

42: computer processing unit (CPU)

43: read only memory (ROM) storing program

44: and 45: random access memories (RAMs); and

46: interface

CPU 42 and ROM 43, which store the programs to be executed by CPU 42,constitute sequential processing means 13 and sensor-data processingmeans 14, both shown in FIG. 1. RAM 44 constitutes sequential filingmeans 13 shown in FIG. 1. RAM 45 temporarily stores the data outputtedfrom sensor means 11. RAM 45 and interface 46 constitute interfacebuffer means 15 shown in FIG. 1.

In FIG. 2, small-scale computer 20 includes key board 47, interface 48,CPU 49, ROM 50, RAMs 51 to 53 and interface 54. CPU 49 and ROM 50, whichstore the programs to be executed by CPU 49, constitute inference enginemeans 25 shown in FIG. 1. RAMs 51 and 52 constitute, respectively,knowledge base means 22 and 23 also shown in FIG. 1. RAMs 51 and 52 canbe altered by operating key-board 47. New data can be added to this databy inputting the new data by means of key-board 47 via interface 48. RAM53 constitutes common data buffer means 23 as shown in FIG. 1. The datastored in RAM 45 of large-scale computer 10 is transferred to RAM 53 viainterface 46. The results obtained by CPU 49 are supplied to CRT 30,through interface 54 and are displayed.

The operation of this embodiment according to the present invention willnow be described, in conjunction with the flow diagram shown in FIG. 3.

(1) Firstly, the first data outputted from sensor means 11 are read in apredetermined sequence by sequential processing means 12, and thenstored in sequential filing means 13 (STEP 1). Actually, this work iscompleted by supplying the first data from sensors 11a, 11b, 11c and soforth to RAM 44, through interface 41, under the control of CPU 42.

(2) The first data stored in sequential filing means 13 are processed byCPU 42, thereby second data showing operation conditions of the blastfurnace being formed. This processing step produces data showing a rateof change, comparison of levels, dispersion of values and integralvalues of the first data within a designated time interval. This work isactually carried out (STEP 2).

(3) The second data obtained in STEP 2 are compared with standard data,thereby providing true-and-false data. The true-and-false data arestored in interface buffer means 15. More specifically, the data arestored in RAM 45 shown in FIG. 2 (STEP 3).

(4) The true-and-false data stored in interface buffer means 15 aretransferred to common data buffer means 23 (STEP 4). More precisely, thedata stored in RAM 45 are transferred, through interface 46, to RAM 53.

(5) Inference engine means 24 infers heat conditions in the blastfurnace, based on the data stored in knowledge base means 21 andknowledge base means 22, and on the true-and-false data stored in commondata buffer means 23 (STEP 5). This work is achieved as CPU 49 executesthe programs, designated by the data stored in RAMs 51 and 52, and inRAM 53.

Knowledge base means 22 is composed of knowledge units necessary forjudging levels of furnace heat conditions, judging levels of transitionof the furnace heat conditions, judging actions and amending the actionsso as to infer efficiently. Each of those knowledge units indicates anoperator's knowledge and experience on the controlling productionprocess, in the form of "If . . . , then . . .". In this embodiment, thereliability of inference is raised by introducing to inference process acertainty factor (CF) value, which indicates the uncertainty degree ofeach rule for the operating production process.

With reference to FIG. 4, inference engine means 24, firstly judgeslevels of furnace heat conditions and levels of transition of thefurnace heat conditions, and then, judges amount of actions, based onthe results of the preceeding judgements. Further, inference enginemeans 24 amends the amount of actions.

(6) Subsequently, the amount of actions amended in STEP 5 is supplied,via interface 54, to CRT 30, and is displayed. At the same time, theamended amount is transferred to control devices 31, the humidity ofblast air to be blown into the blast furnace being controlled.

(7) Then, it is determined whether stop signal has been given or not. If"YES", the processing is stopped. If "NO", it returns to STEP 1 (STEP7). In the latter case, the aforementioned STEPs 1 to 7 are repeated atpredetermined intervals of, for example, 2 minutes.

Factors on Heat Conditions in Furnace

Tuyere Nose Temperature: a temperature of a thermometer buried at an endof a tuyere nose reflects heat conditions in a blast furnace. It isshown that the higher the temperature of the thermometer becomes, thehigher the heat conditions becomes.

Burdern Descend Speed: If an endothermic reaction given by the formula"FeO+C=Fe+CO" proceeds, coke consumption speed becomes fast and theburden descend speed becomes fast. Consequently, the phenomenon that theburden descend speed becomes fast means a furnace heat temperature goesdown.

Furnace Top Gas Temperature: If a furnace top gas temperature becomeshigh, the burden descend speed becomes slow and a furnace heattemperature goes up. If a furnace top gas temperature becomes low, thefurnace heat temperature goes down.

Gas Utilization Ratio: The gas utilization ratio is given by thefollowing formula: ##EQU1## ηco: Gas Utilization ratio CO: COconcentration in top gas (%)

CO₂ : CO₂ concentration in top gas (%)

As CO gas increases, ηco gets lower. Lowering of value of η indicatesincrease of solution loss reaction. Consequently, infurnace heat islowered by means of the endothermic reaction.

Solution Loss Amount: At the infurnace portion of a high temperature of1,000° C. or more, reaction called direct reduction proceeds. Seemingly,iron oxides such as FeO are reduced to Fe by C, but actually, as shownbelow, reactions of formulae (a) and (b) proceed simultaneously, andthey result in formula (c). The formula of (b) is called solution lossreaction. The reaction of the direct reduction is an endothermic one,and the value is exceedingly high enough to show 36,350 Kcal/Kmol. Thisis a fatal factor lowering infurnace heat.

    FeO(s.1)+CO(g)=Fe(s.1)+CO.sub.2                            (a)

    CO.sub.2 (g)+C(s)=2CO(g)                                   (b)

    FeO(S.1)+C(s)=Fe(S.1)+CO(g)                                (c)

When this direct reduction reaction gets active, the percentage of N₂contained in furnace top gas is lowered due to the increase of CO gas.An expert engineer of blast furnace operation catches this phenomenon,based on his experience to make use of it for aid of judging furnaceheat conditions. In the system of the present invention, solution lossreaction amount is computed directly from the furnace top gasconstituent, blast air conditions, molten metal chemical composition asshown below, and is stored in knowledge base.

    S1c=BG·(CO+CO.sub.2)·10.sup.-2 ·(Vbd·0.21.2/22.4+Vbw·Tmoi·10.sup.-3 /18)-A                                                    (1)

    BG=79·Vbd(%N.sub.2)/22.4                          (2)

    Vbd=Vbw·(1-22.4·10.sup.-3 ·Moi/18)(3)

    A=Asi+Amn+Ap                                               (4)

    Asi=2·[%Si]/28·10·12·Prod/1440(5)

    Amn=[% Mn]/55·10·12·Prod/1440   (6)

    Ap=5/2·[%P]/31·10·12·Prod/1440(7)

Vbw: blast air amount [Nm³ /min]

Moi: moisture of blast air [g/Nm³ ]

Tmoi: total moisture of blast air including water blown [g/Nm³ ]

CO, CO₂, N₂ : top gas constituent

Prod: amount of tapped molten metal [T/D]

[%Zi],[%Mn],[%P]: chemical composition of molten metal

Air Blast Pressure: Increase of the air blast pressure indicates thatthe furnace heat is high, while decrease of the air blast pressureindicates that the furnace heat is low.

Si Content in Molten Metal: Si content in molten metal is correlatedwith molten metal temperature. If the molten metal temperature becomeshigh, the Si content in molten metal becomes high.

S Content in Molten Metal: S content in molten metal is reverselycorrelated with molten metal temperature. If the molten metaltemperature becomes high, the S content in molten metal becomes low.

Slag Color: Since molten metal discharged through tap holes includesmolten slag, the molten slag is separated from the molten metal by meansof a skimmer. The separated molten slag is taken out by means of a steelscoop, poured into a vessel filled with water and then rapidly cooled.The color of the cooled slag becomes white-yellow when furnace heat issatisfactory and reduction of iron ores is well done, and the colorturns into black due to increase of FeO concentration in the molten slagwhen the furnace heat is unsatisfactory and the reduction of iron oresare not well done. Accordingly, the action to be taken is judgeddepending on colors of the molten slag and the action is so taken.

Processing Data on Levels of Heat Conditions

Data of tuyere nose temperature, burden descent speed, air blastpressure, furnace top gas temperature, gas utilization ratio andsolution loss amount, each, are supplied every minute. Data suppliedevery minute is hereinafter referred to as one minute data.

(a) Molten Metal Temperature: a balance between a molten metaltemperature presently supplied and a standard level molten metaltemperature is computed. And then, from the balance, a molten metaltemperature level is computed and obtained by using molten metaltemperature membership function.

(b) Tuyere Nose Temperature: a mean value is computed from one minutedata of tuyere nose temperatures supplied from all the thermometersburied in the top ends of all the tuyere noses. One minute data areexponentially smoothed by using the mean value to obtain a one minutedata value. A balance between a one minute data value thus presentlyobtained and a standard level tuyere nose temperature is computed. Andthen, from this balance, a tuyere nose temperature level is computed andobtained by using a tuyere nose temperature membership function.

(c) Burden Descend Speed: a mean value of one minute data of burdendescend speeds is computed from one minute data supplied by sounding ofprobes set in four points towards periphery portions at a throat levelof a blast furnace to measure burden descend speed. One minute data areexponentially smoothed by using the mean value to obtain a one minutedata. A balance between a one minute data value thus obtained and astandard level burden descend speed is computed. And then, from thisbalance a burden descend speed level is computed and obtained by using aburden descend speed membership function.

(d) Air Blast Pressure: a mean value of one minute data of air blastpressures is computed from one minute data supplied by air blastpressure gauges to measure air blast pressures of blowers sending hotair into a blast furnace. One minute data is exponentially smoothed toobtain a one minute data value. A balance between a one minute datavalue thus presently obtained and a standard level air blast pressure iscomputed and then, from this balance an air blast pressure level iscomputed and obtained by using an air blast membership function.

(e) Furnace Top Gas Temperature: a one minute data value is computedfrom furnace top gas temperatures supplied by furnace top gasthermometers set in four points towards periphery portions at a throatlevel of a blast furnace, by means of an exponential smoothingtreatment. A balance between a one minute data value thus presentlyobtained and a standard level furnace top gas temperature is computed.And then, a furnace top gas level is computed and obtained by using afurnace top gas membership function.

(f) Gas Utilization Ratio: One minute data of the gas utilization ratiois obtained from a furnace top gas constituents of CO and CO₂ a gaschromatography. The one minute data are exponentially smoothed to obtaina one minute data value. A balance between a one minute data value thusobtained and a standard level gas utilization ratio is computed. Andthen, from this balance, a gas utilization level is computed andobtained by using a gas utilization ratio membership function.

(g) Solution Loss Amount: One minute data of the solution loss amountare obtained from one minute solution loss amount data measured by a gaschromatography. The one minute data is exponentially smoothed toobtained a one minute data value. A balance between a one minute datavalue thus obtained and a standard level solution loss amount iscomputed. And then, from this balance a solution loss amount level iscomputed and obtained by using a solution loss amount membershipfunction.

Judgement on levels of furnace heat conditions

With specific reference to FIG. 5, process of judging levels of heatconditions in a blast furnace will now be explained in detail.

Knowledge units stored in knowledge base means 21 contain rules formolten metal temperature (KS-109, 110), rules for sensors (KS-103 toKS-108) and human judgement rules (KS-109, 110), as those for thecontrolling production process.

(a) Rules for molten metal temperature

These rules are for judging present levels of furnace heat conditionsfrom a present molten metal temperature.

A rule for molten metal temperature, KS-101 judges furnace heatconditions, based on experiences statistically accumulated in the pastoperation of a blast furnace.

A rule for molten metal temperature, KS-102 judges levels of furnaceheat conditions by means of estimating the highest temperature of moltenmetal presently tapped out. This estimation is based on statisticcalculation of the latest n pieces of molten metal temperature measured.

Certainty factor (CF) values, CF-101 and CF-102, each, are obtained fromrules for molten metal temperature KS-101 and KS-102, each. The rules ofKS-101 and KS-102 are given weights. In this weighting, for example, v₁is given to KS-101, and v₂ to KS-102. The sum of v₁ plus v₂ is set tobe 1. A judgement value for levels of furnace heat conditions, CF-120 isobtained, consideration of the weights of v₁ and v₂, from CF-101 andCF-102.

(b) Rules for sensors

Among these rules, there are tuyere nose temperature rule 103, a burdendescent speed rule 104, a furnace top gas temperature rule 105, a gasutilization ratio rule 106, a solution loss amount rule 107, and apressure rule for air blown into a blast furnace 108. For each of rulesfrom 103 to 108, a level of furnace heat conditions is respectivelycomputed. The level further consists of 7 levels as hereinafterexplained. Certainty factor (CF) value is computed for each of the 7levels. Weights of v₃, v₄, v₅, v₆, v₇ and v₈ are also given to therules, each, and the sum of v₃ to v₈ equals to 1. A judgement value forlevels of furnace heat conditions, CF-130 is obtained, in considerationof the weights of v₃ to v₈, from CF-103 to CF-108.

More specifically, computation of levels of furnace heat conditionsoutputted from sensors will be explained.

In the case of level 7, CF value for level 7 is computed and obtained bysumming each of the following:

    (CF value for Level 7 of Tuyere Nose Temperature)×(Weighing on Tuyere Nose Temperature)

    (CF Value for Level 7 of Burden Descend Speed)×(Weighing on Burden Descend Speed);

    (CF Value for Level 7 of Air Blast Pressure)×(Weighing on Air Blast Pressure);

    (CF Value for Level 7 of Furnace Top Gas)×(Weighing on Furnace Top Gas);

    (CF Value for Level 7 of Gas Utilization Ratio)×(Weighing on Gas Utilization Ratio); and

    (CF Value for Level 7 of Solution Loss Amount)×(Weighing on Solution Loss Amount).

CF Value for each of levels 6, 5, 4, 3, 2 and 1 is also computed andobtained similarly to the case of that for level 7. As described above,a level of furnace heat conditions, based on the information outputtedfrom sensors which is taken into consideration of a CF valuecorresponding to levels 7 to 1, each concerned, is computed andobtained.

(c) Two other judgement rules

These rules includes a tuyere condition rule and a slag color rule.

The tuyere condition rule inputs one selected from the items consistingof "as previously set", "obscure" "good", "ordinary" and "bad"(judgement on levels of furnace heat conditions CF-109). Similarly, theslag color rule inputs one selected from the items consisting of "aspreviously set", "obscure", "color" number 1 to 5: (1; good, 2;ordinary, and 3 to 5; "bad") (judgement on levels of furnace heatconditions, CF-110). A judgement on levels of furnace heat conditions,CF-140 of certainty factor values is obtained, in consideration of thelevels of CF-109 and CF-110. Each of the items ranks grades 1 to 7.Consequently, the judgement on each of the levels is determined bycombination of items with grades.

(d) Judgement on levels of furnace heat conditions

A certainty factor value (CF-150), as a sum of each level of furnaceheat conditions, is judged from CF-120 drawn out of the rules for moltenmetal temperature, and from CF-130 out of the rules for sensors. In thisjudgement, CF-120 and CF-130 are given weights of V₁ and V₂. The sum ofV₁ and V₂ equals to 1. Thus, a judgement on levels of furnace heatconditions, CF-150 of certainty factor values, is obtained, inconsideration of the weights of V₁ and V₂ as shown in Table 1. In thiscase, the levels of furnace conditions is composed of levels of 1 to 7.

                  TABLE 1                                                         ______________________________________                                        Level of Furnace Evaluation of Heat                                           Heat Conditions  Temperature                                                  ______________________________________                                        7                Most Heated                                                  6                More Heated                                                  5                Ordinary                                                     4                Cooled                                                       3                More Cooled                                                  2                Most Cooled                                                  1                Extraordinarily Cooled                                       ______________________________________                                    

For example, when a certainty factor value of levels of furnaceconditions "1" (Extraordinarily Cooled) or "2" (Most Cooled) is apredetermined value of Wx or over, a judgement rule is applied, whereinCF value for each of levels 1 to 7 for furnace heat conditions (ajudgement on levels of furnace heat conditions CF-160) is computed bysumming CF-140 and CF-150.

More specifically, computation of furnace heat conditions will beexplained.

In the case of level 7, the computation is carried out by summing eachof the following:

    (CF Value of Level 7 of Molten Metal Temperature)×(Weighing on Molten Metal Temperature); and

    (CF Value for Level 7 of Furnace Heat Conditions, based on Sensors)×(Weighing on Furnace Heat Conditions, based on Sensors).

In the case of level 6, the computation is carried out by summing eachof the following:

    (CF Value for Level 6 of Molten Metal Temperature)×(Weighing on Molten Metal Temperature); and

    (CF Value for Level 6 of Furnace Heat Conditions, based on Sensors)×(Weighing on Furnace Heat Conditions, based on Sensors).

CF value for each of levels 5, 4, 3, 2 and 1 is also computed andobtained similarly to those cases of levels 7 and 6. As described above,a level of furnace heat conditions having a CF value corresponding tolevels 7 to 1, is computed and obtained.

For the purpose of judgement on levels of furnace heat conditions,knowledge units are classified into three categories, i.e., rules formolten metal temperature, those for sensors and those for two otherjudgements, by reason of the following:

1. Object of control, itself is molten metal temperature;

2. The molten metal temperature can be detected, by

nature, approximately every 20th minute at best. The treatment of theinformation is different from that of the information outputted fromsensors, since the sensors can gather information data every minute;

3. The molten metal temperature starts with low temperature, due tohearth bottom and troughs of a blast furnace being cooled, and increasesgradually. Consequently, when the highest molten metal temperature in atap, for example, is to be controlled, levels of furnace heat conditionsmust be judged, these additional affecting factors being taken intoconsideration;

4. When operation is successful, the behavior of the molten metaltemperature and the work of sensors are correlated though there is timedelay. But, when, for example, molten slag within the blast furnaceincreases in volume, thereby distribution of top gas being peripherallyprevailed, the correlation between the behavior and the work becomesreverse. In this case, it is preferable to judge the levels of furnaceheat conditions, separately based on rules for molten metal temperatureand rules for sensors, each.

5. Other judgement rules are composed of two rules. In the case ofoperation being abnormal, it is recommendable to use the two rulesseparately. This easily enables certainty factor values for the abnormalconditions to be strengthened, and information unobtainable throughsensor means to be grasped so as to decide an optimum action inresponse. Of course, in the case of operation being normal, automaticcontrol is principally employed without use of other judgement.

Examples for Judgement on Levels of Furnace Heat conditions

(a) Molten Metal Temperature: For example, in the case of a molten metaltemperature being 1,490° to 1,500° C., the molten metal temperaturelevel is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.1                                                                     6     0.2                                                                     5     0.5                                                                     4     0.4                                                                     3     0.3                                                                     2     0.2                                                                     1     0.1                                                              ______________________________________                                    

(b) Tuyrere Nose Temperature: For example, in the case of a tuyere nosetemperature being 140° C. to 150° C., the tuyere nose temperature levelis represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.1                                                                     6     0.3                                                                     5     0.5                                                                     4     0.4                                                                     3     0.2                                                                     2     0.1                                                                     1     0                                                                ______________________________________                                    

(c) Burden Descend Speed: For example, in the case of a burden descendspeed being 0.1 to 0.105 m/min., the burden descend speed level isrepresented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.3                                                                     6     0.4                                                                     5     0.7                                                                     4     0.5                                                                     3     0.4                                                                     2     0.2                                                                     1     0.1                                                              ______________________________________                                    

(d) Air Blast Pressure: For example, in the case of an air blastpressure being 3.80 to 3.805 Kg/cm², the air blast pressure isrepresented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.3                                                                     6     0.4                                                                     5     0.7                                                                     4     0.6                                                                     3     0.4                                                                     2     0.2                                                                     1     0.1                                                              ______________________________________                                    

(e) Furnace Top Gas Temperature: For example, in the case of a furnacetop temperature being 160° C. to 170° C., the furnace top gastemperature level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.2                                                                     6     0.4                                                                     5     0.7                                                                     4     0.3                                                                     3     0.2                                                                     2     0.1                                                                     1     0                                                                ______________________________________                                    

(f) Gas Utilization Ratio: For example, in the case of a gas utilizationratio being 50.0 to 50.2%, the gas utilization ratio level isrepresented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.1                                                                     6     0.3                                                                     5     0.5                                                                     4     0.4                                                                     3     0.2                                                                     2     0.1                                                                     1     0                                                                ______________________________________                                    

(g) Solution Loss Amount: For example, a solution loss amount being 36.0to 37.0 Kmol/min, the solution loss amount level is represented asfollows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               7     0.1                                                                     6     0.3                                                                     5     0.5                                                                     4     0.4                                                                     3     0.2                                                                     2     0.1                                                                     1     0                                                                ______________________________________                                    

(h) Weighing on Furnace Heat Conditions: FIG. 7 of the drawings shows aflow of weighing levels of furnace heat conditions, giving an example ofthe weighing.

Processing of Data on Levels of Transition of Furnace Heat Conditions

(a) Molten Metal Temperatures: A balance between a molten metaltemperature of molten metal previously tapped and that of molten metaltapped latest is computed, and then, from the balance, a level oftransition of furnace heat conditions is computed and obtained by usinga molten metal temperature transition level membership function.Furthermore, from a balance between a molten metal temperature of moltenmetal tapped immediately before the previously tapped molten metal and amolten metal temperature of the previously tapped molten metal, a moltenmetal temperature level is computed and obtained by using a molten metaltransition level membership function.

(b) Tuyere Nose Temperature: A balance between a one minute data valueof a tuyere nose temperature obtained at a present moment and thatobtained 60 minutes before the present moment measurement. From thisbalance, a tuyere nose temperature transition level is computed andobtained by using a tuyere nose temperature transition membershipfunction.

(c) Burden Descend Speed: From a balance between a one minute data valueof a burden descend speed obtained at a present moment and that obtained60 minutes before the present moment measurement a burden descend speedtransition level is computed and obtained by using a burden descendtransition membership function.

(d) Air Blast Pressure: From a balance between a one minute data valueof an air blast pressure obtained at a present moment and that obtained60 minutes before the present moment measurement, an air blast pressuretransition level is computed and obtained by using an air blast pressuretransition membership function.

(e) Furnace Top Gas Temperature: From a balance between a one minutedata value of a furnace top gas temperature obtained at a present momentand that obtained 60 minutes before the present moment measurement, afurnace top gas temperature transition level is computed and obtained byusing a furnace top gas temperature transition membership function.

(f) Gas Utilization Ratio: From a balance between a one minute datavalue of a gas utilization ratio obtained at a present moment and thatobtained 60 minutes before the present moment measurement, a gasutilization ratio transition level is computed and obtained by using gasutilization ratio transition membership function.

(h) Solution Loss Amount: From a balance between a one minute data valueof a solution loss amount obtained at a present moment and that obtained60 minutes before the present moment measurement, a solution amounttransition.

(h) Si Content in Molten Metal: From a balance between a Si contentvalue in molten metal of the previous tap and that in molten metal ofthe latest tap, a transition level of a Si content value in molten metalis computed and obtained by using transition level membership functionof a Si content value in molten metal.

(i) S Content in Molten Metal: From a balance between a S content inmolten metal of the previous tap and that in molten metal of the latesttap, a transition level of a S content in molten metal is computed andobtained by using transition level membership function of a S contentvalue in molten metal.

Judgement on Levels of Transition of Furnace Heat Conditions

As shown in FIG. 6, for judgement on levels of transition of heatconditions in the blast furnace, knowledge units stored in knowledgebase means 22 contain rules for molten metal temperature (KS-201, -202),rules for sensors (KS-203 to KS-208) and the other rules (KS-209, 210),as those for the controlling production process. For each of thoserules, certainty factor (CF) values of levels of C1 to C5 as shown inTable 3 is computed.

                  TABLE 3                                                         ______________________________________                                        Levels of Transition of                                                       Furnace Heat Conditions                                                                          Evaluation                                                 ______________________________________                                        C5                 Considerable Increase                                      C4                 Increase Tendency                                          C3                 No Change                                                  C2                 Decrease Tendency                                          C1                 Considerable Decrease                                      ______________________________________                                    

(a) Rules for molten metal temperature

These rules for molten metal temperature are a rule for comparison ofthe latest temperature of molten metal with the highest molten metaltemperature in a previous tap (KS-201), and a rule for comparison of thehighest molten metal temperature in a previous tap with the highestmolten metal temperature in a tap immediately before the previous tap.

More specifically, computation of levels of transition of furnace heatconditions, based on molten metal temperature will be explained.

CF value for level 5 is computed and obtained by summing each of thefollowing:

    {CF Value for Level 5 of Molten Metal Temperature Transition (1), based on a Balance between Molten Metal Temperatures of Present Tap (1) and Previous Tap}×{Weighing on Molten Metal Temperature Transition (1)}; and

    {CF Value for Level 5 of Molten Metal Temperature Transition (2), based on a Balance between Molten Metal Temperatures of Previous Tap and Tap before Previous Tap}×{Weighing on Molten Metal Temperature Transition (2)}.

As described above, a level of furnace heat conditions, based on moltenmetal temperatures, having a CF value corresponding to levels 5 to 1, iscomputed and obtained.

(b) Rules for sensors

Among these rules, there are a tuyere nose temperature rule, a burdendescent speed rule, an air blast rule, a gas utilization rule, asolution loss amount rule and a furnace top gas temperature rule. Fromeach of the rule, CF values (CF-203 to CF-208), each, are computed andobtained. The CF values rank five levels.

(c) The other rules

The other rules are a rule for transition of contents of silicon andsulfur (KS-209) and a rule for index of furnace conditions (KS-210). CFvalues (CF-209, -210), each, are computed for the rules.

(d) Judgement on levels of transition of furnace heat conditions

In the case of the rules for molten metal temperature, the rules ofKS-201 and KS-202 are given, respectively, weights of W₁ and W₂. The sumof the weights equals to 1. A judgement on levels of transition of heatconditions in the blast furnace, CF-220 is obtained, in consideration ofthe weights, from CF-201 and CF-202.

Similarly, the rules of KS-203 to KS-210 are given, respectively,weights of w₃, w₄, w₅, w₆, w₇, w₈, w₉ and w₁₀, and the sum of theweights of w₃ to w₁₀ is 1. A judgement on levels of transition of heatconditions in the blast furnace, CF-230 is obtained, in consideration ofthe weights, from CF-203 to CF-210.

And then, a CF value (CF-240) of levels of transition of heat conditionsin the blast furnace for each of five levels, is obtained by summing CFvalues of CF-220 and CF-230.

More specifically, computation of levels of transition of furnace heatconditions will be explained.

Levels of transition of furnace heat conditions are computed andobtained from a transition level of furnace heat conditions, based onmolten metal temperatures, a transition level of furnace heatconditions, based on sensors and a transition level of furnace heatconditions based on compositions of molten metal.

For example, a level 5 is computed and obtained by summing each of thefollowing:

    (CF Value for Level 5 of Transition Level of Furnace Heat Conditions, based on Molten Metal Temperatures)×(Weighing on Transition of Furnace Heat Conditions based on Molten Metal Temperatures);

    (CF Value for Level 5 of Transition of Furnace Heat Conditions, based on Sensors)×(Weighing on Transition of Furnace Heat Conditions, based on Sensors); and

    (CF Value for Level 5 of Transition of Furnace Heat Conditions, based on Sensors)×(Weighing on Transition of Heat Conditions, based on Sensors).

CF value for each of levels 4 to 1 is also computed and obtainedsimilarly to the case of level 5. As described above, a level oftransition of furnace heat conditions having CF value corresponding tolevels 5 to 1, is computed and obtained.

Examples for Judgement on Levels of Transition of Furnace HeatConditions

(a) Molten Metal Temperature: For example, in the case of a molten metaltemperature at a present moment being by 30° C. lower than that of theprevious tap, the molten metal temperature transition level isrepresented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0                                                                       4     0.1                                                                     3     0.15                                                                    2     0.3                                                                     1     0.6                                                              ______________________________________                                    

(b) Tuyere Nose Temperature: For example, in the case of a tuyere nosetemperature transition being -0.15° to -0.10° C./min., the tuyere nosetemperature transition level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.1                                                                     4     0.2                                                                     3     0.3                                                                     2     0.4                                                                     1     0.5                                                              ______________________________________                                    

(c) Burden Descent Speed: For example, in the case of a burden descentspeed transition being 0.0005 to 0.001 m/min./min., the burden descentspeed transition level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.1                                                                     4     0.2                                                                     3     0.3                                                                     2     0.4                                                                     1     0.5                                                              ______________________________________                                    

(d) Air Blast Pressure For example, in the case of an air blast pressuretransition being 0.0005 to 0.001 kg/cm² /min., the air blast pressurelevel is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.5                                                                     4     0.4                                                                     3     0.3                                                                     2     0.2                                                                     1     0.1                                                              ______________________________________                                    

(e) Furnance Top Gas Temperature: For example, in the case of a furnacetop gas temperature transition being 1° to 2° C./min., the furnace topgas temperature level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.5                                                                     4     0.4                                                                     3     0.3                                                                     2     0.2                                                                     1     0.1                                                              ______________________________________                                    

(f) Gas Utilization Ratio: For example, in the case of a gas utilizationratio transition being -0.015 to -0.10%/min., the gas utilization ratiotransition level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.1                                                                     4     0.2                                                                     3     0.3                                                                     2     0.4                                                                     1     0.5                                                              ______________________________________                                    

(g) Solution Loss Amount: For example, in the case of a solution lossamount transition being 0.2 to 0.25 Kmol/min., the solution loss amounttransition level is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0.1                                                                     4     0.2                                                                     3     0.3                                                                     2     0.4                                                                     1     0.5                                                              ______________________________________                                    

(h) Si content in Molten Metal: For example, in the case of a Si contentin molten metal of the latest tap being reduced 0.15 to 0.2% from thatin molten metal of the previous tap, the transition level of a Sicontent in molten metal is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0                                                                       4     0.1                                                                     3     0.15                                                                    2     0.3                                                                     1     0.6                                                              ______________________________________                                    

(i) S Content in Molten Metal: For example, in the case of a S contentin molten metal of the latest tap being reduced by 0.015 to 0.02% fromthat in molten metal of the previous tap, the transition level of a Scontent is represented as follows:

    ______________________________________                                               Level CF Value                                                         ______________________________________                                               5     0                                                                       4     0.1                                                                     3     0.15                                                                    2     0.3                                                                     1     0.6                                                              ______________________________________                                    

(j) Weighing on Levels of Transition of Furnace Heat Conditions: FIG. 8of the drawing shows a flow of weighing levels of transition of furnaceheat conditions, giving an example of the weighing.

Judgement on actions

Based on CF values for levels of furnace heat conditions (L1 to L7) andfor levels of transition of furnace heat conditions (C₁ to C₅) obtainedin such a manner as described in the above, amount of actions is judgedas shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                Grade (j)                                                                       Levels of Transition of                                                       Furnace Heat Conditions                                             Grade (i)   5       4      3      2    1                                      ______________________________________                                                  7     a.sub.75                                                                              a.sub.74                                                                           a.sub.73                                                                             a.sub.72                                                                           a.sub.71                             Level     6     a.sub.65                                                                              a.sub.64                                                                           a.sub.63                                                                             a.sub.62                                                                           a.sub.61                             of        5     a.sub.55                                                                              a.sub.54                                                                           a.sub.53                                                                             a.sub.52                                                                           a.sub.51                             Furnace   4     a.sub.45                                                                              a.sub.44                                                                           a.sub.43                                                                             a.sub.42                                                                           a.sub.41                             Heat      3     a.sub.35                                                                              a.sub.34                                                                           a.sub.33                                                                             a.sub.32                                                                           a.sub.31                             Conditions                                                                              2     a.sub.25                                                                              a.sub.24                                                                           a.sub.23                                                                             a.sub.22                                                                           a.sub.21                                       1     a.sub.15                                                                              a.sub.14                                                                           a.sub.13                                                                             a.sub.12                                                                           a.sub.11                             ______________________________________                                    

A CF value represented by "a_(ij) " is given by the following formula:

    a.sub.ij =CF value for grade i of Furnace Heat Conditions×CF value for grade j of Transition of furnace Heat Conditions

"a_(ij) " thus obtained corresponds to amount of actions shown in Table5.

                  TABLE 5                                                         ______________________________________                                        A          Moisture of air blast to be increased                                         by 5 gr/Nm.sup.3                                                   B          Moisture of air blast to be increased                                         by 3 gr/Nm.sup.3                                                   C          no action                                                          D          Moisture of air blast to be decreased                                         by 3 gr/Nm.sup.3                                                   E          Moisture of air blast to be decreased                                         by 5 gr/Nm.sup.3                                                   F          Moisture of air blast to be decreased                                         by 5 gr/Nm.sup.3, and blast temperature to                                    be increased                                                       G          Amount of blast air to be decreased,                                          and coke ratio to be increased                                     ______________________________________                                    

CF values for amount of actions shown in Table 4 are obtained by theaforementioned formula. However, if each CF value for levels of furnaceheat conditions, or for levels of transition of furnace heat conditionsis less than a predetermined value, it is desirable to count such a CFvalue as zero. In addition, if a CF value for amount of actions shown inTable 4 is more than a predetermined value, it is recommendable thatamount of actions is outputted so as to make CF values in order ofnumbers small to large for operation guide. And, if the same action isoutputted in plurality, it is recommendable that the largest CF value isto be displayed to an operator.

More specifically, judgement on action will be explained.

If, for example, CF value for a level of furnace heat conditions and CFvalue for a level of transition of furnace heat conditions aredetermined, as shown in Table below judgement on action amount isjudged.

    ______________________________________                                                   CF Values for Levels of Transition                                            of Furnace Heat Conditions                                                    5      4      3        2    1                                                 0.2    0.3    0.5      0.2  0.1                                    ______________________________________                                                7      0.3   0.06   0.09 0.15   0.06 0.03                             CF Values                                                                             6      0.5   0.10   0.15 0.25   0.10 0.05                             for Levels                                                                            5      0.7   0.14   0.21 0.35   0.14 0.07                             of Furnace                                                                            4      0.4   0.08   0.12 0.20   0.08 0.04                             Heat    3      0.3   0.06   0.09 0.15   0.06 0.03                             Conditions                                                                            2      0.2   0.04   0.06 0.10   0.04 0.02                                     1      0.1   0.02   0.03 0.05   0.02 0.01                             ______________________________________                                    

Amendment to amount of actions

An action amount, based on judgement on action; is amended when aneffect to sensors or furnace heat conditions by an action already taken,or an additional affecting factor still remains. As such an additionalaffecting factor, drop of unreduced ore and sudden change of cokemoisture are considered.

Action amount is correction amount necessary to obtain desirable furnaceheat conditions, and is arranged, i.e., increased or decreased, by atleast one selected from the following:

(a) arrangement of moisture amount contained in blast air which is blownin through a tuyere;

(b) arrangement of water amount contained in blast air which is blown inthrough a tuyere;

(c) arrangement of temperature of blast air which is blown in through atuyere;

(d) arrangement of tar amount which is blown in through a tuyere;

(e) arrangement of heavy oil which is blown in through a tuyere;

(f) arrangement of blast air which is blown in through a tuyere; and

(g) arrangement of coke amount which is charged through a top of a blastfurnace.

Action is taken subject to a preferential order at present practice,increase or decrease of moisture contained in blast air is ranked as thefirst order. Therefore, the amount of the action is expressed in termsof amount of moisture contained in blast air being blown in. When actionis taken as means other than the increase or decrease of moisture, theamount of the action is converted into an amount of moisture which isincreased or decreased.

According to the present invention, true-and-false data are prepared onthe basis of the data outputted from sensor means 11 provided for ablast furnace, and then, inference, as an artificial intelligence, iscarried out in comparison of the true-and-false data with knowledge baseformed by accumulated experiences on the operation of the blast furnace.This gives advantages in that, (a) experience on the past operation canbe made full use of, (b) a small capacity of computer processing unitscan be used, and (c) response to the changes the blast furnace undergoesduring its life can easily be attained.

Example

Control of heat conditions was carried out for 20 days, employing ablast furnace with 4664 m³ inner volume, according to a method of thepresent invention. Judgements on furnace heat conditions were made every20th minute and actions were instructed, based on the results of thejudgements.

An example of the above operation results is shown in FIG. 9.

The operation of the blast furnace was carried out with air blast of6,500 Nm³ /min. and at a coke ratio of 514 kg/T-pig. Changes of typicaldata outputted from the sensor means, the results of judgement on levelsof furnace heat conditions and the results of judgement on transition oflevels of furnace conditions are illustrated in FIG. 9.

Operational action in response to furnace heat conditions was carriedout by means of controlling amount of steam. The amount of steamrepresented by a broken line is in compliance with instructions obtainedfrom judgements on actions, and that of steam by a solid line, incompliance with actual actions.

Actions of increasing amount of steam (a₁, a₂, a₃ and a₄), and actionsof decreasing amount of steam (b₁, b₂, b₃ and b₄) were instructed, inaccordance with judgements on actions. Actions of a₁, a₂, a₄, b₁, b₂ andb₄ were actually taken.

The highest molten metal temperature representing a tap, wasapproximately 1500° C. The dispersion of molten metal temperatures wasreduced from 9.16° C. to 6.24° C. by application of the presentinvention to control of furnace heat conditions. The range (maximumvalue minus minimum value) of molten metal temperatures was also reducedfrom 24.2° C. to 14.3° C.

What is claimed is:
 1. A method for controlling operation of a blastfurnace, wherein the blast furnace includes a sensor means which outputsfirst data, corresponding to conditions in said blast furnace whichcomprises the steps of:supplying a central processing unit with saidfirst data outputted from said sensor means; storing standard datacorresponding to predetermined values of data corresponding to saidconditions in said blast furnace; preparing true-and-false data bycomparing said first data with said standard data; storing informationon operation and control characteristics of said blast furnace based onaccumulated actual knowledge and experience of at least one operator ofsaid blast furnace, said information being stored as data in a knowledgebase means; inferring and judging heat conditions in said blast furnace,on the basis of said true-and-false data and said data in said knowledgebase means and formed by accumulated experience on the operation of theblast furnace; and controlling heat conditions in the blast furnace inaccordance with results of said inferring and judging step.
 2. Themethod according to claim 1, wherein said step of inferring and judgingheat conditions in the blast furnace includes inferring and judginglevels of heat conditions in the blast furnace.
 3. A method according toclaim 2, wherein said step of inferring and judging levels of heatconditions includes inferring and judging levels of heat conditions,from molten metal temperature.
 4. The method according to claim 2,wherein said step of inferring and judging levels of heat conditionsincludes inferring and judging levels of heat conditions, based on dataoutputted from the sensor means provided for the blast furnace.
 5. Themethod according to claim 2, wherein said step of inferring and judginglevels of heat conditions includes inferring and judging levels of heatconditions, based on tuyere condition and slag color.
 6. The methodaccording to claim 4, wherein said inferring and judging, based on dataoutputted from the sensor means includes inferring and judging, based onat least one selected from the group consisting of:(a) data representingtuyere nose temperature; (b) data representing burden descent speed; (c)data representing air blast pressure blown into the blast furnace; (d)data representing gas utilization ratio; (e) data representing solutionloss amount pressure; and (f) data representing furnace top gastemperature.
 7. The method according to claim 1, wherein said step ofinferring and judging heat conditions in the blast furnace includesinferring and judging levels of transition of heat conditions in theblast furnace.
 8. The method according to claim 7, wherein said step ofinferring and judging levels of transition of heat conditions includesinferring and judging levels of transition of heat conditions, frommolten metal temperature.
 9. The method according to claim 7, whereinsaid step of inferring and judging levels of transition of heatconditions includes inferring and judging levels of transition of heatconditions, based on data outputted from the sensor means provided forthe blast furnace.
 10. The method according to claim 7, wherein saidstep of inferring and judging levels of transition of heat conditionsincludes inferring and judging levels of transition of heat conditions,based on Si and S content in the molten metal.
 11. The method accordingto claim 9, wherein said inference and judgement, based on dataoutputted from the sensor means includes inferring and judging, based onat least one selected from the group consisting of:(a) data representingtuyere nose temperature; (b) data representing burden descent speed; (c)data representing air blast pressure blown into the blast furnace; (d)data representing gas utilization ratio; (e) data representing solutionloss amount pressure; and (f) data representing furnace top gastemperature.
 12. The method according to claim 1, wherein said step ofinferring and judging heat conditions in the blast furnace includesinferring and judging levels of heat conditions, and inferring andjudging levels of transition of heat conditions.
 13. The methodaccording to claim 1, which further comprises processing data outputtedfrom the sensor means.
 14. The method according to claim 1, wherein saidstep of inferring and judging heat conditions in the blast furnaceincludes computing certainty factor values.
 15. The method according toclaim 1, wherein said step of controlling heat conditions in the blastfurnace operation includes judging action amount from the results ofjudgement on level of furnace heat conditions and from the results ofjudgement on transition of furnace heat conditions.
 16. The methodaccording to claim 15, wherein said action amount includes beingamended, in consideration of effect by an action already taken and anadditional affecting factor.